Tuesday’s special election in a central Ohio congressional district will provide tangible evidence of where the battle for the House stands three months out from the midterms.

Both parties have deployed their 2018 playbooks for the final special election before November, and its importance far exceeds the typical House race: If Democrat Danny O’Connor prevails, it will be a sign that Democrats are poised to take back the House next year, despite an avalanche of Republican outside money.

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But if Troy Balderson, the GOP nominee, wins, it will give Republicans hope that the House isn’t lost, and that President Donald Trump can still help the party get out the vote this fall.

The Ohio special election isn’t the only key race on the ballot on Tuesday. There are also primaries in Kansas, Michigan, Missouri and Washington state — with hypercompetitive gubernatorial contests in Kansas and Michigan, and nominees set to be picked for a number of House races on the November battlefield.

Polls close at 7:30 p.m. Eastern time in the Ohio special election. In the primaries, polls close statewide at 8 p.m. in Missouri, 9 p.m. in Michigan and Kansas, and 11 p.m. in Washington.

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Here are five things to watch as the results roll in:

What will Ohio tell us about the GOP playbook of Trump and Pelosi?

The special election in Ohio will test the potency of boiling down a House race to two candidates not on the ballot: Trump and Nancy Pelosi, a pair of polarizing figures that each party hopes will drive turnout.

Trump campaigned alongside Balderson last weekend, aiming to juice support for the state senator in a race that’s tightened into single digits, according to public and private polling. But the president’s rally — along with a negative tweet about Ohio’s favorite son and NBA star, LeBron James — also risks alienating well-educated Columbus suburbanites who prefer Gov. John Kasich to the president and could swing the special election.

But Republicans believe that “Trump stoked the base. He energized them this weekend, so that will help balance out the intensity on the Democratic side,” said Mark Weaver, a Republican strategist based in Ohio. “The race is closer than it ought to be, but this is still a Republican district. And the fundamentals are on Troy’s side.”

Republicans also tried to tie O’Connor to Pelosi in TV ads, a strategy the GOP has used in special elections throughout the past year and is prepared to replicate in the fall. O’Connor tried to cut into the anti-Trump-Republican voting bloc by signaling his independence from his national party, pledging not to support Pelosi in his first and last TV ads. But in the middle, O’Connor flubbed his answer on Pelosi in an MSNBC interview, which Republicans have deployed against him in their own ads.

If Democrat Danny O’Connor prevails, it will be a sign that Democrats are poised to take back the House next year. | Scott Olson/Getty Images

The results out of Tuesday’s special election will give each party hard data on how a red-leaning seat performs, just three months out from the November midterms. But Tuesday isn’t only about a data point: O’Connor and Balderson will face off again in the general election, and the winner of the special will certainly have a leg up in the race for a full term.

How does Trump’s last-minute endorsement in Kansas alter the governor’s race?

Kris Kobach was an early Trump ally, advising the then-candidate on immigration policy and protecting against voter fraud. “One of the things that struck me when I first met him and spoke to him for the first time is just how intellectually hungry he was,” Kobach, the Kansas secretary of state, told POLITICO just before the 2016 election of his first meeting with Trump.

So when Trump endorsed Kobach’s gubernatorial campaign in a tweet just 20 hours before the polls open, some might have wondered, “What took so long?”

But Trump had good reason to stay on the sidelines. Kobach is challenging incumbent Gov. Jeff Colyer, the former lieutenant governor who was elevated to the top job because Trump tapped then-Gov. Sam Brownback for a State Department post.

Moreover, the president had been urged to stay on the sidelines by the Republican Governors Association and some White House advisers, who fear that Kobach could be defeated in a general election. (And even if Kobach wins, some Republicans believe he would drag down the party’s other candidates, including in the competitive 2nd and 3rd congressional districts targeted by Democrats.)

Kansas might be a solidly red state in national politics — Trump won it by 27 points in 2016 — but Brownback was wildly unpopular by the time he left office. After nearly a decade of losses to Brownback and his allies, GOP moderates have been reasserting their power in recent years. (The 95-year-old Bob Dole endorsed Colyer in a tweet of his own Monday afternoon.)

But Colyer isn’t alone on the ballot as a Kobach alternative, and Jim Barnett — the 2006 GOP nominee for governor — has emphasized Colyer’s ties to Brownback to stake his claim to the moderate lane. If Kobach wins a narrow victory on Tuesday, Trump will likely be able to take credit for his victory — and any resulting GOP heartburn over Kobach’s prospects against the expected Democratic candidate, state Sen. Laura Kelly.

Will Trump’s Michigan endorsements pay off?

Kobach isn’t the only Trump-endorsed candidate on a primary ballot on Tuesday. The president is also backing two men running statewide in Michigan, one of the three states Trump flipped to propel him to an upset victory in the 2016 presidential race.

For governor, Trump picked state Attorney General Bill Schuette over Lt. Gov. Brian Calley. Polls show Schuette with a double-digit lead in the contest, and few observers are expecting an upset from Calley, who is backed by outgoing moderate Gov. Rick Snyder.

Trump has also endorsed in the Senate race, backing businessman John James, an African-American Army veteran, over self-funder Sandy Pensler. In a reaffirmation of his initial endorsement last month, Trump, in a tweet Monday called James a “potential Republican Star.”

Polling is limited, but James appears to have moved past Pensler, whose campaign turned ugly in the final days. A racially charged Pensler ad that began airing last week said James “thinks he’s a celebrity, a rock star. But peel back the onion, and you find Jesse Jackson.”

Can Bernie Sanders and Alexandria Ocasio-Cortez play kingmaker in Democratic primaries?

It’s been six weeks since Alexandria Ocasio-Cortez shocked the political world by ousting Rep. Joe Crowley of New York in a Democratic primary, and liberals are angling for their next victory.

There are a number of targets on Tuesday — most prominently Abdul El-Sayed, a 33-year-old physician running for governor in Michigan against an establishment-backed candidate, former state Sen. Gretchen Whitmer.

Ocasio-Cortez campaigned with El-Sayed in late July, while Sanders visited this past weekend. The final polls gave Whitmer a double-digit lead over El-Sayed and a self-funding candidate, Shri Thanedar — but those surveys are two weeks old.

Back in July, Sanders and Ocasio-Cortez actually hit the road together to campaign for two congressional candidates in Kansas, including Brent Welder, a former Sanders campaign staffer seeking to take on Rep. Kevin Yoder (R-Kan.) in the fall. Of the three major Democratic candidates running in the suburban Kansas City district, Welder is viewed as the most liberal — and Republicans are confident they can paint him as out-of-step with a traditionally Republican area that has recoiled at Trump’s GOP.

Ocasio-Cortez is also backing a liberal Democrat seeking to unseat an incumbent in a primary Tuesday: Cori Bush, who is running against Rep. Lacy Clay (D-Mo.) in a St. Louis-based district. Bush, an ordained minister and registered nurse, supported Sanders in the 2016 presidential primary. But the Vermont senator hasn’t reciprocated and backed her against one of his former House colleagues.

What are Democrats’ chances to win a battleground House seat in Washington?

Democrats have been waiting for a clean shot at Dave Reichert’s House seat for nearly a decade. The suburban Seattle district votes for Democrats at the presidential level, but Reichert — the popular former sheriff of King County — has won reelection easily in recent cycles.

That prompted lots of Democratic optimism when Reichert announced his retirement last year. Republicans landed their top recruit, however, and it was a familiar face: Dino Rossi, who has narrowly lost three statewide elections in his career, including a 133-vote defeat against Christine Gregoire for governor in 2004. Rossi has been a fundraising machine, bringing in $3 million for the race through mid-July.

Tuesday’s primary will tell us a lot about the race. Like California, Washington uses the top-two primary system, in which all candidates run together on the ballot, and the top two finishers advance to the general election, regardless of party. There are 12 candidates on the ballot Tuesday in Washington’s 8th District, and Rossi is expected to finish first.

The real competition is for second place, with three Democrats thought to be the top contenders: Kim Schrier, a pediatrician, attorney Jason Rittereiser and former public-health official Shannon Hader.

But sharp observers will be also paying close attention to the share of the vote earned by Rossi and the two other Republicans running on Tuesday — and whether the district is poised to flip after decades of GOP representation.